1. Field of the Invention
This invention relates to a signal processing apparatus, a method of processing signals, a recording medium recording a signal process, and a program for processing signals, and relates, for example, to a signal processing apparatus, a method of processing signals, a recording medium recording a signal process, and a program for processing signals, preferably used for enhancing texture surrounded by edges, without excessively enhancing the edges within an image.
2. Related Art
Conventionally, methods of enhancing contrast by converting gradation and methods of enhancing high frequency components are known to improve contrast (difference in brightness) and sharpness (clearness at an edge) in an image generated by an imaging element such as CCD (Charge Coupled Device), and CMOS (Complementary Metal-Oxide Semiconductor) in video cameras and the like.
As a contrast enhancement method, tone curve adjustment methods are known for converting a pixel level of each pixel with a function having a predetermined input-output relation (hereinafter this is referred to as level conversion function), and further, histogram equalization methods are known for adaptively changing a level conversion function in accordance with frequency distribution of pixel levels.
As high frequency component enhancement methods, a method called “unsharp mask” is known for extracting an edge and enhancing the extracted edge.